The present invention relates to 3-D woven textile products and to methods and machines for making the same. These woven products may be included in other structures, e.g. coated with thermoplastic or thermosetting resins or embedded in other materials such as foams, elastomers, rubbers, polymers etc.
Composite sandwich structures can be produced from three-dimensional textile preforms that are manufactured using conventional velvet or face-to-face weaving technology. The woven fabric has two distinct separated layers, which are joined together with a xe2x80x98pilexe2x80x99 yarn during the fabric forming process.
In subsequent processing, the two layers form the surfaces of a sandwich panel and the pile forms the core. The mechanical properties of these structures can be tailored to a limited extent through choice of surface and pile fiber architecture. However a feature inherent to conventional weaving processes, and hence face-to-face weaving, is that the fiber is predominantly oriented at the primary weaving axes of warp and weft, which are usually orthogonal to each other. As a result, the mechanical properties of the preforms are restricted. The shear strength between the surfaces can be enhanced to a limited degree by altering the sequence of weaving of the pile yarns to form an xe2x80x98angle interlockxe2x80x99 arrangement, or xc2x145xc2x0 warp pile. However, the processing restrictions of standard weaving technology limits this pile configuration, and hence elevates shear strength in the warp direction only.
To expand the application of 3-D textile sandwich preforms, there needs to be more options for engineering their mechanical performance by incorporating multiaxial fiber orientation both on the surface and in the pile.
The present invention relates to a method of producing angled weft oriented pile in sandwich preforms.
In particular the present invention relates to a woven fabric structure comprising two woven fabric sheets each made up of warp and weft threads, the fabric sheets being parallel to and facing each other, the two fabric sheets being linked to each other by first uniting threads, the direction of at least some of said first uniting threads having a component in the weft direction which makes an angle of between xc2x115 and xc2x175xc2x0 with the plane of the fabric sheets, whereby a first uniting thread trapped in a first position in a first of the two fabric sheets is trapped in the second of the two fabric sheets at a second position equivalent to at least one warp thread removed from the first position.
The present invention may also provide a woven fabric structure comprising two woven fabric sheets each made up of warp and weft threads, the fabric sheets being parallel to and facing each other, the two fabric sheets being linked to each other by first uniting threads, the direction of at least some of said first uniting threads having a component which lies in a plane parallel to the planes of the first and second fabric sheets and which makes an angle of between xc2x115 and xc2x1165xc2x0 with the direction of the warp threads, whereby a first uniting thread trapped in a first position in a first of the two fabric sheets is trapped in the second of the two fabric sheets at a second position displaced in the warp and/or weft direction from the first position. The distance of the displacement is at least one warp or weft thread separation distance, for example is preferably two or more warp and/or weft thread separation distances.
The present invention may also provide a method of weaving a fabric structure comprising two woven fabric sheets each made up of warp and weft threads, the fabric sheets being parallel to and facing each other, comprising the steps of:
linking the two fabric sheets to each other by first uniting threads, the direction of at least some of said first uniting threads having a component in the weft direction which makes an angle of between xc2x115 and xc2x175xc2x0 with the plane of the fabric sheets by trapping a first uniting thread in a first position in a first of the two fabric sheets and subsequently trapping the same thread in the second of the two fabric sheets at a second position displaced in the weft direction from the first position. The distance of the displacement is at least one warp thread separation distance, for example is preferably two or more warp thread separation distances.
The present invention may provide a method of forming a woven fabric structure comprising two woven fabric sheets each made up of warp and weft threads, the fabric sheets being parallel to and facing each other, comprising the steps of: linking the two fabric sheets to each other by first uniting threads, the direction of at least some of said first uniting threads having a component which lies in a plane parallel to the planes of the first and second fabric sheets and making an angle of between xc2x115 and xc2x1165xc2x0 with the direction of the warp threads by trapping a first uniting thread trapped in a first position in a first of the two fabric sheets and trapping the same first uniting thread in the second of the two fabric sheets at a second position displaced in the warp and/or weft direction equivalent from the first position. The distance of the displacement is at least one warp or weft thread separation distance, for example is preferably two or more warp and/or weft thread separation distances.
The present invention may also provide a weaving loom adapted to carry out any of the methods in accordance with the present invention. In particular, the loom may be adapted to manipulate pile threads in front of the reed by transferring one or more pile threads in the weft direction and trapping these at the transferred position in one of a first and second fabric sheet being woven simultaneously on the loom.